Ultrashort wave circuit



@ energy such as described hereinabove.

Patented Aug. 30, 1938 UNITED STATES ULTRASHORT WAVE. CIRCUIT Nils E. Lindenblad, Port Jefferson, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Original application January 26, 1933, Serial No. 653,579, now Patent No. 2,011,943, dated August 20, 1935. Divided and thisap-plication January 4, 1935, Serial No. 355- 7 Claims.

This invention relates to apparatus for undulating electrical energy and especially to a receiving system for ultra short wave length radiated electromagnetic energy. (Division of my United States Patent No. 2,011,943, granted August 20, 1935, on an application filed January 26, 1933.)

Ultra short wave length oscillations have been produced by the use of electron discharge devices having their control electrodes at high positive potentials relative to the other electrodes of the devices. The production of ultra short wave oscillations under such conditions may be ascribed tothe fact that electrons attracted towards the control electrode or grid pass through the grid structure and, upon approaching a relatively negatively charged anode, are caused to return towards the grid, partly due to the attractive action of the positive charge on the grid and partly due to the repelling effect of the negatively charged anode. The returning electrons again rush through the grid only to approach the cathode, where the combined space charge as well as the attracting force of the grid causes the electrons to repeat the cycle outlined. The oscillations so produced are of ultra short wave lengths and are known as Barkhausen-Kurz oscillations.

In order to modulate such oscillations, audio frequency modulation has been directly applied to the oscillatory energy so produced, and the ultra short wave length energy has been modulated by relatively low radio frequency oscillations modulated at audio frequencies giving what is known as double modulation of the ultra short Wave length oscillations.

It is an object of'my present invention to provide receiving systems for the collection, heterodyning and amplification, demodulation and translation of modulated ultra short wave length More specifically, it is an object of my invention to provide the combination, in an ultra short wave receiving system, of an antenna for collecting ultra short wave length energy, a tuning circuit especially adapted for resonating the collected ultra short Wave length energy, one or more oscillator-detector electron discharge devices for the heterodyning and amplification of the resonated energy, and means to demodulate and translate the amplified intermediate frequency energy.

Still a further object of the present invention is to provide for heterodyning and amplification purposes, one or more electron discharge devices having their control electrodes or grids maintained. at high positive potentials relative to the unidirectional potentials on the other electrodes of the devices, adjustably coupled to the tuning circuit for resonating the collected energ in combination with, preferably, a regenerative detector for demodulating the energy amplified by the devices.

I have found that by the use of a tuned radio frequency regenerative circuit for demodulating the amplified'intermediate frequency oscillations, the regenerative circuit will give approximately the same amplification whether double modulation is employed at the transmitting end or the transmitted oscillations are only modulated directly by audio frequency energy. In the event of double modulation, the intermediate frequency circuit at the receiving end should, of course, be

tuned to the intermediate frequency used at the transmitting end of the system. If desired, in the case of double modulation, a radio frequency ampl'ifier, rather than a regenerative circuit, tuned to the intermediate frequency may be used for further amplification.

A better understanding of-the present invention may be had by referring to the accompanying drawing which is given merely by way of illustration of the invention and is not to be considered in any way limitative thereof. In the drawing;

Fig. 1 illustrates a receiving system for ultra short wave length radiated electromagnetic energy, a single tube oscillator-detector-amplifier functioning on the Barkhausen-Kurz principle being used before the regenerative detection of the amplified energy; and

Fig. 2 illustrates a system similar to that shown in Fig.1, wherein collected energy is amplified in a push-pull type of amplifier before demodulation.

Referring to Fig. 1, ultra short wave length energy is collected upon an antenna 5, and fed through a transmission line 2 to a tuning circuit l. The energy so collected is resonated in the tuning circuit and applied to the oscillator-detector-amplifier 5 which beats with the incoming signal energy to produce an intermediate frequency and to which is coupled a regeneratively connected detector circuit 8 which demodulates the amplified energy. A suitable audio frequency amplifier 9, coupled to the intermediate frequency regenerative circuit 8, supplies energy to a trans lating device such as phones It wherein the transmitted signal is reproduced. It should be noted that circuit 8 is not adjusted for oscillations, but only for regenerative purposes.

The tuning circuit 4 is composed of substantially linear conductors l2, l4 connected together by metallic U-shaped slides or trombone slides l6, l8 which provide for variation in tuning of the tuning circuit 4. The use of U-shaped conductors for varying the tuning of the tuning circuit is advantageous in that the length of the tuning circuit and hence the tuning of it can be varied without having any inductive or bothe-r- 1 some tail ends in the circuit.

The linear conductors are closely spaced in order to prevent undesired pick-up, and are terminated by radio frequency short circuiting means in the form of condensers 6, 3 which prevent the application of high positive control electrode potentials to the anode of tube 5, the high positive grid potential being derived from a suitable potentiometer 26. By varying the position of condenser 3 along conductors l2, M, or. by adjusting the junction points of transmission line 2 along the conductors 12, M, the junction point of the transmission line 2, relative to the standing wave on the tuning system, can be varied and, consequently the impedance of the line 2 can be accurately matched, allowing of maximum energy fiow into the tuning circuit.

Oscillator-detector-amplifier tube 5 is also mounted so that it can be variably adjusted along the length of conductors l2, 14 so that, as described, it can be made to impose a variable load on the tuning circuit, whereby the oscillating and regenerative properties of the tube 5, Whose control electrode is maintained at a high positive potential relative to the other electrodes of the devices, can be controlled.

Terminating the tuning circuit by means of a by-pass condenser 6 prevents, as already indicated, the application of undesired grid potential to the plate or anode of tube 5.

The output circuit of tube 5 is completed through a coil 1 to a potentiometer 22' which supplies through the coil 1, a suitable potential to the anode of tube 5, ranging from a low positive potential to negative potentials. Coil 1 couples the output electrode or plate of tube 5 to the regenerative circuit 8 which is made to have constants corresponding to an appreciably longer wave length, and, in the case of at the transmission end, the transmission of double modulated energy should be tuned to correspond to the intermediate frequency used at the transmitter.

The modulation component of the received energy will appear in. transformer 24, by-passed by a suitable radio frequency condenser 26.

This component may then be amplified in a suitable low frequency amplifier 9 and translated by a suitable translating device Ill.

The regenerative detector, as illustrated, comprises an electron discharge device 28 having a variable feed back coil 30 coupled to the input coil 32 and to the. output coil 1. Proper biasing potential for the control electrode of tube 28 is maintained by action of the condenser and resistance arrangement 34.

Experimentation, with the arrangement described, has shown it to amplify equally well double modulated waves such as alluded to, or ultra short waves modulated directly by low frequency signalling currents. Attention is directed to the fact that in the reception of ultra short wave length energy directly modulated by low frequency energy, operation of the system may be attributed to the fact that there is interaction between the high frequency tuning cirquently,

necessarily result suit 4 and regenerative circuit 8, of the lower frequency, the energy supplied by tube 5 being modulated by energy of a frequency correspond ing to the tuning of circuit 8 as well as being regeneratively amplified in circuit 8. During operation, circuit 8 is preferably not adjusted for the generation of oscillations, but solely for regenerative amplification.

A modified receiving system for ultra. short wave length energy, is illustrated schematically in Fig. 2. Ultra short wave length energy, collected upon an antenna 40, fed to transmission lines 42 through the inductive action of loops 44, 46, is supplied to a resonating circuit 48. Resonating. or tuning circuit 48 contains U-shaped metallic slides 50, 52. The conductors 62, 64 of tuning circuit 58 are connected through trombone slides5il, 52 to the anodes of tubes 58, 60, whose control electrodes are maintained at a relatively high positive potential relative to the electrodes of the devices by voltage potentiometer 66. The control electrodes are connected together by conductors 68, ill having trombone slides 54, 56 therein, for varying the effective length of the conductors and hence the tuning of the control electrode circuit l2. The positive potential to the grids, of course, is supplied to the circuit 12 at a voltage nodal point thereof as indicated.

The adjustment of all of the trombone slides will cause an eifective variation in the position of push-pull connected electron discharge devices 58, 60 along conductors 62, 64 and 68, 10.

With the connections as described, and with the anodes maintained at a negative potential by the action of voltage potentiometer M, the anode circuit will be the most sensitive part of the apparatus, as a consequence of which the incoming energy is applied thereto. Consevariations in the received current will cause variations in anode current through the primary of transformer i6 whose secondary may be coupled to a suitable receiver '58 actuating a translating device 80.

Receiver 18 may be of the regenerative type such as described in connection with Fig. l, or it may simply be an audio frequency amplifier in which case transformer 75 should be so designed as to derive from the anode potential supply lead, the audio frequency component which will from the application of the received potentials to the desired circuits. The tubes 58, 60 in this case, therefore will not only have an amplifying action, but will also give a demodulating or detecting action of the received energy. Moreover, in the case of double modulation at the transmitter, receiver 18 may comprise a tuned radio frequency amplifier, tuned to the intermediate frequency as there will be an intermediate frequency component appearing in the primary of transformer 15. The amplifier should then be followed by a suitable demodulator or' detector.

Although I have described in detail some modifications of my invention, it, of course, is not to be limited thereto as it may be altered in several respects readily apparent to those skilled in the art, and, therefore, my invention is to be limited in scope only by the appended claims.

What is claimed is:

1. In an ultra short wave receiver, an energy collecting system, a heterodyne circuit coupled to said energy collecting system and comprising an electron discharge device oscillator-detector producing oscillations of a frequency different from the frequency of the incoming signal wave, said device having anode, cathode and grid electrodes, and means for maintaining said grid at a high positive potential and said anode at a much less potential relative to said cathode, whereby said device functions on the braking field principle to produce a frequency lower than that of the Waves received on the antenna.

2. Ultra high frequency receiving apparatus comprising an energy collecting system, an electron discharge device oscillator-detector coupled to said energy collecting system, said device producing oscillations of a frequency different from the frequency of the incoming signal wave and having anode, cathode and grid electrodes, and means for maintaining said grid at a high positive potential and said anode at a much less potential relative to said cathode, whereby said device functions on the braking field principle to produce an intermediate frequency, and a regenerative amplifier-detector circuit coupled to the output of said device.

3. An ultra short wave receiving system comprising an antenna for receiving ultra high frequencies, an electron discharge device oscillatordetector coupled to said antenna, said detector device producing oscillations of a frequency different from the frequency of the incoming signal wave and having an anode, a cathode and a grid, means for maintaining said grid at a high positive potential and said anode at a much lower potential whereby said device functions on the braking field principle to produce an intermediate frequency, and means coupled to the output of said oscillator-detector for translating said intermediate frequency to audible sound waves.

4. In combination in an ultra short wave receiving station, an energy collector circuit for receiving the incoming signal wave, an ultra high frequency electron discharge tube oscillator for producing oscillations of a frequency different from the frequency of the incoming wave, circuit connections coupling said oscillator and said energy collector circuit, said oscillator comprising an electron discharge device having an anode, cathode and control electrode, and having means for maintaining the control electrode at a positive direct current bias potential relative to said cathode and anode, means for tuning said oscillator, an output circuit tuned to a frequency equal to the difference between said two frequencies, and a regenerative amplifier-detector circuit connected to said output circuit and arranged to receive oscillations of said last frequency.

5. In combination in an ultra short wave receiving system, an antenna tuned to the incoming signal wave, an ultra high frequency detector-heterodyning oscillator for producing an intermediate frequency, said oscillator comprising an electron discharge device having an anode, cathode and control electrode, and having means for maintaining the control electrode at a positive direct current bias potential relative to the cathode and anode, a pair of connections, one of which is connected to said anode and the other to said control electrode, a tuning condenser connected across said pair of connections, said antenna being coupled across said pair of connections, an output circuit coupled to one of said connections and means for detecting the energy in said output circuit.

6. In combination in an ultra short wave receiving system, an antenna, an ultra high frequency detector-heterodyning oscillator for producing an intermediate frequency, said oscillator comprising an electron discharge device having an anode, cathode and control electrode, and having means for maintaining the control electrode at a positive direct current potential relative to the cathode and anode, a pair of connections one of which is in circuit with said anode and the other in circuit with said control electrode, said antenna being adjustably coupled to said pair of connections near one end thereof, ,a line adjustment impedance connected across said one end of said pair of connections, said anode and control electrode being coupled to said pair of connections, near the other end thereof, a second impedance connected across said last end, a trombone tuning slide in each of said pair of connections intermediate their ends, an output circuit coupled to one of said connections, and a regenerative amplifier-detector circuit coupled to said output.

7. An ultra short wave receiver system comprising a pair of valves each having cathode,

anode, and grid electrodes, means for applying relatively high positive potentials to the grids of said valves relative to their respective cathodes, means for applying much lower potentials to the anodes of said valves than are applied to said grids whereby said valves function on the braking field principle, a dipole antenna, a conductor system interconnecting the anodes of the valves and coupling same to said dipole, a conductor system interconnecting the grids of the valves, a conductor system in circuit with the cathodes of the valves, and a translating circuit coupled to one of said conductor systems whereby audible reception may be obtained.

NILS E. LINDENBLAD. 

